Question

我想以编程方式向视图添加自定义按钮，并设置该按钮的约束。这是我的代码：

    let button = SummaryButton(frame: CGRect(x: 0, y: 0, width: 36, height: 36))
    button.setTitle("1", for: .normal)
    button.addTarget(self, action: #selector(daysButtonPressed), for: .touchUpInside)
    button.translatesAutoresizingMaskIntoConstraints = false
    daysView.addSubview(button)

    NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: daysView, attribute: .leading, multiplier: 1.0, constant: 20).isActive = true
    NSLayoutConstraint(item: button, attribute: .centerX, relatedBy: .equal, toItem: daysView, attribute: .centerX, multiplier: 1.0, constant: 0).isActive = true
    NSLayoutConstraint(item: button, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .height, multiplier: 1.0, constant: 36).isActive = true
    NSLayoutConstraint(item: button, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .width, multiplier: 1.0, constant: 36).isActive = true

我根本看不到按钮。如果我删除约束，我可以看到它，但位置不正确。

我是如何设置约束的？我想添加到视图的左侧。

Answer 1

删除centerX约束，因为您已有前导

NSLayoutConstraint(item: button, attribute: .centerX, relatedBy: .equal, toItem: daysView, attribute: .centerX, multiplier: 1.0, constant: 0).isActive = true

并从视图顶部添加前50个点

NSLayoutConstraint(item: button, attribute: .top, relatedBy: .equal, toItem: daysView, attribute: .top, multiplier: 1.0, constant: 50).isActive = true

以编程方式向视图添加自定义按钮

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